Method For Transmitting And Damping Torques

ABSTRACT

A method for the transmission and damping of a mean torque with a superposed alternating torque in an arrangement having an input and an output. The mean torque and superposed alternating torque are transmitted along a path from the input to the output. A slip arrangement is provided in the torque path between the input and the output for transmitting mean torque and superposed alternating torque and for generating a speed slip between an input speed and an output speed in the path. The slip arrangement provides a maximum of an external activation of the speed slip in the area of the maxima of at least one periodic oscillation component of the alternating component and provides a minimum of an external activation of the speed slip in the area of the minima of at least one periodic oscillation component of the alternating component.

CROSS REFERENCE TO RELATED APPLICATIONS

This is a U.S. national stage of application No. PCT/EP2017/062832,filed on May 29, 2017. Priority is claimed on German Application No.DE102016211958.3, filed Jun. 30, 2016, the content of which isincorporated here by reference.

BACKGROUND OF THE INVENTION 1. Field of the Invention

The present invention is directed to a method for the transmission ofand for the damping of a mean torque with a superposed alternatingtorque in a torque transmission arrangement for the powertrain of amotor vehicle with an input area and a downstream output area.

2. Description of the Prior Art

A method of the above type in a torque transmission arrangement for thepowertrain of a motor vehicle is known from DE 10 2008 009 135 A1. Inthis method, a friction clutch is provided between an internalcombustion engine and a shiftable transmission, and the friction clutchis controlled such that a speed difference of a resonance speed rangepresent at the friction clutch is reduced during startup to a greaterextent than when not controlled.

It is disadvantageous in this prior art method that only the startingprocess and the shuddering known through the starting process are to bereduced. However, this method does not possess the capacity to damptorsional vibrations, which are caused by the internal combustion engineand which occur in a constant driving state.

SUMMARY OF THE INVENTION

Therefore, it is an object of one aspect of the present invention toprovide a method for reducing torsional vibrations in a torquetransmission device which effects an advantageous reduction in torsionalvibrations chiefly after the starting process.

The invention is directed to a method for the transmission of anddamping of a mean torque with a superposed alternating torque in atorque transmission arrangement for a powertrain of a motor vehiclecomprising an input area which is rotatable around a rotational axis(A), and an output area, which is rotatable around a rotational axis(B), wherein the mean torque with the superposed alternating torque istransmitted along a torque path from the input area to the output area,the input area of the torque transmission arrangement rotates at aninput speed around the rotational axis (A), and the output area of thetorque transmission arrangement rotates at an output speed around therotational axis (B), at least the input speed is composed of a meanspeed and a superposed alternating component, the alternating componentmay be described approximately through a superposition of periodic speedoscillations whose frequencies have a substantially whole number ratiowith the firing frequency, wherein each of these periodic oscillationshas a minimum and a maximum, wherein a slip arrangement is provided inthe torque path between the input area and the output area fortransmitting the mean torque with the superposed alternating torque andfor generating a speed slip between speed ne and speed na in the torquepath, wherein the slip arrangement provides a maximum of an externalactivation of the speed slip in the area of the maxima of at least oneperiodic oscillation component of the alternating component and providesa minimum of an external activation of the speed slip in the area of theminima of at least one periodic oscillation component of the alternatingcomponent. Further torsional vibration damping units such as, forexample, a first spring set and/or a second spring set and a damper unitcan be arranged between the input area and the output area upstream ofthe slip arrangement. This is particularly advantageous because thealternating torques coming from the input area of an internal combustionengine, for example, are pre-filtered. The slip arrangement aims atreducing the remaining residual alternating torques, optimally even tozero. In order to achieve this, the method according to the inventionprovides that more slip is permitted in case a maximum externalactivation of the slip arrangement is carried out in the area of amaximum of a periodic oscillation of the superposed alternating torqueand that less slip is permitted in case a minimum external activation ofthe slip arrangement is carried out in the area of a minimum of aperiodic oscillation of the superposed alternating torque. This meansthat the slip arrangement, which can be formed, for example, by a slipclutch or by a multiple disk clutch, obtains a hydraulic signal from theexternal activation in the form of a lower hydraulic pressure, which canresult in a reduced pressing force on the multiple disk clutch and canaccordingly lead to increased slip, that is, an increase in the speeddifference. In the case of slip reduction, the external activationshould send a hydraulic signal to the slip clutch in such a way that, inthis case, a hydraulic pressure is increased and the pressing force onthe slip clutch is accordingly likewise increased, which leads to areduction in slip in the slip clutch. The maximum in the superposedalternating torque can be counteracted in this way. The externalactivation for achieving the slip reduction and slip increase may alsobe referred to as slip modulation. In this regard, the frequency of theslip modulation depends on the use of drive unit, for example, theinternal combustion engine. When using a four-stroke internal combustionengine, a frequency range of from 23 Hertz to 60 Hertz is advantageous.When using a four-cylinder/stroke engine, the use of a frequency rangefrom about 33 Hertz to 66 Hertz is advantageous. When using asix-cylinder four-stroke internal combustion engine, the use of afrequency range from 50 Hertz to 100 Hertz is advantageous.

In a further advantageous embodiment form, it is provided that theexternal activation of the slip arrangement is carried out by ahydraulic unit. In case the slip arrangement is constructed as afriction disk clutch, for example, the hydraulic clutch release systemcan be used for this purpose in an economical manner.

It can also be advantageous when the external activation of the sliparrangement is carried out by an electric unit. This can be carried outin a purely electrical manner or also electromagnetically.

In a further advantageous variant, the external activation is suitableto provide a modulation range of from 23 Hz to 50 Hz or a range of from33 Hz to 66 Hz or a range of from 50 Hz to 100 Hz at the sliparrangement.

It may also be advantageous to use the slip arrangement as a startingelement. This saves on further component parts and is thereforeeconomical.

However, a starting element can also be provided in addition to the sliparrangement. The slip arrangement can be configured explicitly tofunction for optimal slip without the slip clutch having to take onstarting situations as well.

A further advantageous configuration provides that the slip arrangementand/or the starting element are/is constructed as a friction clutch oras a multiple disk clutch or as a hydrodynamic clutch or as a disconnectclutch in hybrid drives or as a dual clutch or as a triple clutch or isconstructed as a clutch or a brake in conjunction with a planetary gearunit.

Further, rotational axis (A) and rotational axis (B) can extendcoaxially or so as to be offset relative to one another. Especially invehicles with rear-wheel drive and longitudinally mounted front engine,the two rotational axes (A) and (B) extend coaxial to one another. In afront-wheel drive with transversely mounted engine, rotational axis (A)usually extends at an offset with respect to rotational axis (B).

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be described in more detail in the followingreferring to diagrams. The embodiment examples shown in the drawingsmerely represent preferred constructions and do not limit the scope ofthe invention. The scope of the invention is defined uniquely by theappended claims.

The drawings show:

FIG. 1 is a schematic view of a powertrain as prior art;

FIG. 2 is an advantageous schematic view of a powertrain;

FIG. 3 is deflected torque diagram;

FIG. 4 is an advantageous schematic view of a powertrain;

FIG. 5 is a preferred topology in a schematic view;

FIG. 6 is a basic wiring diagram of a slip clutch;

FIG. 7 is a deflected torque diagram;

FIG. 8 is a slip speed plotted over time;

FIG. 9 is a friction coefficient plotted over slip speed;

FIG. 10 is a friction coefficient plotted over time;

FIG. 11 is a diagram of sine wave of Fa;

FIG. 12 is a diagram of trapezoidal wave of Fa;

FIG. 13 is a diagram of sine wave of Fa of higher order;

FIG. 14 is a further diagrams;

FIG. 15 is a diagram of input speed at the slip arrangement at anoperating point; and

FIG. 16 is a friction coefficient plotted over slip.

DETAILED DESCRIPTION OF THE PRESENTLY PREFERRED EMBODIMENTS

Like or identically functioning component parts are designated by likereference numerals in the following.

Before commenting on FIG. 1, it should be noted that present-daytorsional vibration decoupling systems for passenger automobiles alsoprovide speed-adaptive dampers in addition to spring-mass arrangements,for example, a dual mass flywheel. In addition, a reduction in torquefluctuations in the internal combustion engine can be and is carriedout, at least in powertrains with wet starting elements, via slip in thestarting element. The technique utilized for this purpose in which aslip controller adjusts a predetermined mean slip speed is referred toin the following as “active slip mode 1”. A method is presented in thefollowing for controlling a clutch in a passenger vehicle powertrainwhich is designated “active slip mode 2” and which in particular shallmake it possible to achieve an appreciably better decoupling at the samemean slip speed and, therefore, with the same friction losses than aslipping clutch according to the prior art or at least to achieve alevel of decoupling equivalent to conventional systems while usinglighter and less expensive components for pre-decoupling, for example,spring sets and mass dampers.

FIG. 1 shows a torque transmission arrangement 1 in an automaticpowertrain of a motor vehicle according to the prior art containing atorsional vibration damping unit 15 with speed-adaptive damper 6. Therelevant masses, stiffnesses and the starting element are arranged asfollows, the depiction extending only through the transmission. The restof the powertrain is not visible. A converter lockup clutch 72 isarranged at the input area 25 of the torsional vibration damping unit15.

The speed-adaptive damper 6 is positioned at an intermediate mass 3between a first spring set 10 and a second spring set 20. This topologyhas the following disadvantages with respect to decoupling of torsionalvibration. If the converter lockup clutch 72 is operated with a clutchslip, this reduces the torque fluctuations that are conducted into thetorque transmission arrangement 1. Owing to the fact that the speed ofthe components on the output side of the converter lockup clutch 72, andtherefore also the speed of the mass damper 6, is lower by the adjustedslip speed than, for example, an engine speed of the drive unit 50, thetuning of the mass damper 6 to the engine order is no longer correct sothat the mass damper 6 operates progressively worse as slip increases.The second spring set 20 provides a spring stiffness between therelatively high mass inertia of the mass damper 6 and the likewiserelatively heavy transmission 33. If the mass damper 6 were linkeddirectly to a transmission input shaft 100 then, given the moments ofinertia and shaft stiffnesses that are usually present, the result wouldbe vibrational nodes, as they are called. This means that at certainspeeds, also depending on gear, the mass damper in the vibration systemdoes not undergo any excitation and accordingly cannot establish anyreaction torque and, consequently, cannot contribute to decoupling ofrotational irregularities. At the corresponding speed, this manifestsitself through an appreciable increase in the residual rotationalirregularity (see the dashed line in the top speed area shown in FIG.3). While this is prevented with the existing topology, an intermediatemass resonance which is unfavorable with respect to decoupling ofrotational irregularities can develop through the relatively high massmoment of inertia of the intermediate mass 3 and mass damper 6 ininterplay with the stiffnesses of the spring sets 10 and 20.

FIG. 2 shows a more advantageous topology of the components in FIG. 1.This topology is characterized in that the second spring set 20 isarranged on the primary side with respect to the mass damper 6 resultingin the following advantages. For one, a pre-decoupling upstream of themass damper 6 is improved by a reduction in the combined stiffness ofthe two series-connected spring sets 10 and 20 such that the mass damper6 can be constructed more compactly and the system can operatesupercritically already at low speeds as is clearly shown by thedash-dot line in FIG. 3. Further, the intermediate mass 3 is appreciablysmaller without the link to the mass damper 6 so that no interferingintermediate mass resonance occurs in the operating range. Further, theconverter lockup clutch 72 is arranged on the output side of the torquetransmission arrangement 1 between the mass damper 6 and thetransmission 33. This is advantageous because the order tuning of themass damper 6 is not impaired by the clutch slip. The formation of theabove-described vibrational nodes is also mitigated or prevented throughthe clutch slip of the converter lockup clutch 72 as is shown by thedotted line in FIG. 3.

To facilitate comparison, the arrangement shown in FIG. 2 uses basicallythe same schematic construction and the same quantity of subassemblies,in particular spring sets, as FIG. 1.

However, it will be appreciated that this is only exemplary.Functionally, other constructions of the torsional damper 10, 20, forexample, are also possible, inter alia as single-row or multiple-rowdual mass flywheel. The mass damper 6 can also be constructed indifferent ways, particularly advantageously as a Sarrazin type, Salomontype, or DFTvar type speed-adaptive mass damper.

FIG. 3 shows the deflected torque over speed of a prior art torquetransmission system, one variant without slip and one variant with slipmode 2.

FIG. 4 shows a further topology arrangement as has already beendescribed in FIGS. 1 and 2, but with only one spring set 10, in thiscase as a dual mass flywheel with a one-row spring set.

FIG. 5 shows an advantageous topology for torsional vibration reductionin the powertrain. Pre-decoupling of rotational irregularities refershere to a system which reduces the rotational irregularity upstream ofthe slippable clutch 30. As in the concrete example given above, thiscan comprise an arrangement of torsion springs, masses and mass dampers.However, other principles are also possible such as, for example, arotational irregularity decoupling with two parallel torque transmissionpaths and a coupling arrangement, a gas spring torsional damper, or anarrangement of centrifugal springs.

The required slippable clutch 30 can also be a starting clutchsimultaneously. However, this is not absolutely necessary. The startingclutch can otherwise be placed at any other position in the powertrain.However, the slippable clutch can just as easily be one or more clutchesof the transmission which, depending on gear, perform tasks in gearshifting and/or decoupling of rotational irregularities by slipping. Thetype of transmission, for example, automatic transmission (AT), dualclutch transmission (DCT), automated manual transmission (AMT),shiftless transmission, or manual transmission (MT) and the constructionof the powertrain as front-wheel, rear-wheel or all-wheel drive, also inhybrid construction, are optional. Particularly in MT and DCTtransmissions the described topology is already standard, but not incombination with AT transmissions. However, particularly in manualtransmissions but also in dry dual clutch transmissions the startingclutch used is not suitable over the long term for performing a functionfor rotational irregularity decoupling through slip. To this extentalso, the suggested construction is novel for these powertrains.

FIG. 6 shows a simplified schematic diagram of a slippable clutch 30according to an improved method, namely, clutch slip mode 2.

A substantially improved decoupling can be achieved even at low speedwith the above-described topology with identical stiffness values of thespring set 10, 20, and even clutch slip mode 1 acts effectively tofurther improve decoupling or to prevent vibrational nodes. However, theclutch slip generally leads to friction losses, which can take onunacceptable values at high engine torque and high slip speed increasingfuel consumption and, therefore, CO2 exhaust and the generated frictionheat which must be dissipated have a limiting effect in this case.

The object of one aspect of the present invention is to enhance thedecoupling effect of slip at low slip speed. This is achieved in thatthe torque transmittable by the clutch is actively modulated. For thisreason, this process is called active slip mode 2. A force which isadjusted by a slip controller in order to achieve a determined meanspeed difference between an input side 31 of the slip arrangement 30 andan output side 32 of the slip arrangement 30 is designated by F0. At astationary operating point, F0 may be considered constant. To thisextent, the transmittable torque of the slip clutch 30 is calculated as:

M_tr=F_0·r·μ(n_slip),

wherer=mean friction radiusμ=friction coefficient of clutch linings which depends on the slip speedn_slip.

Fa(α,) designates an additional force whose amplitude depends on areference angle α and a phase shift β. The dependency can be given by asine function, for example. The reference angle can be, for example, thecrankshaft position. For tuning to the main engine order in afour-cylinder four-stroke engine, this would mean:

F_a(α,β)=F_a·sin(2a+β)

Accordingly, the transmittable torque is calculated as:

M_tr=

[F

0+F_a·sin(2a+β)]·r·μ(n_slip).

FIG. 7 shows the effect of the modulation of the clutch torque on thetorsional vibration decoupling of the main engine order. Compared toslip mode 1, the rotational irregularity is once again substantiallyreduced by slip mode 2 at the same mean slip speed and withcorrespondingly identical friction losses.

FIGS. 8, 9 and 10 illustrate how the functioning of active slip mode 2is derived. Because of nonlinear relationships and non-harmonicexcitation in the actual powertrain, the way the modulation of thetransmittable clutch torque works in relation to the decoupling ofrotational irregularities can only be graphically derived under highlysimplified conditions. To this end, let it be assumed that a rotationalirregularity at the input side of the clutch is purely sinusoidal in themain order, in this case the first engine order. At a constant clutchforce F0, there is in this example a mean slip of 5 RPM which oscillatesaround the mean value with an amplitude of 4 RPM (compare FIG. 8). Thecurve of the friction coefficient of the slip clutch over slip islinearized in this area, which is represented by the solid line in FIG.9. Accordingly, a sinusoidal curve over time also results for thefriction coefficient as is shown in FIG. 10. The mean frictioncoefficient in this case is μ_0=0.105 and the amplitude is μ_a=0.012.

For the transmittable torque with modulation in the main order, in turn:

M_tr=

[F

0+F_a·sin(a+β)]·r·[μ_0+μ_a·sin(α)].

Angle α is calculated as α=2·π·n·t, where n=speed and t=time.With an optimal phase shift β=180°=π, it follows: sin (α+n)=sin (α).Through expansion of M_tr:

M_tr=r[F_0μ_0+(F_0μ_a−F_aμ_0)sin(α)−F_aμ_a sin {circumflex over ( )}2

(a)

].

With sin {circumflex over ( )}2

(α)=½(1−cos(2α)

), it follows:

M_tr=r·[

(F

_0μ_0−(F_aμ_a)/2)+(F_0μ_aμ_0)sin(α)+(F_aμ_a)/2 cos(2α)]

The summands in the square brackets of this term can be assigned todifferent orders:

Zeroth order: F_0μ_0−(F_aμ_a)/2

Mean Torque

To obtain the same mean transmittable torque, different forces F_0 arenecessary (adjusted by the slip controller) for different subtrahends(F_a μ_a)/2.

First order: (F_0μ_a−F_aμ_0)sin(α)

Main Order in this Example

Can be completely canceled under the simplified assumptions in thechoice of F_a=(F_0μ_a)/μ_0. The effect of one aspect of the invention isgrounded in this.

Second order: (F_aμ_a)/2 cos(2α)

The modulation results in a new order with doubled modulation frequency.However, the amplitude of this order is comparatively small and, inaddition, higher orders of the powertrain are damped better than lowerorders so that the positive effect of reducing the main order ispreponderant. This derivation is a highly simplified model. Becauseconditions diverge from real-world conditions, a complete cancellationof the main engine order is impossible in practice with this method, butan appreciable reduction is possible as can be seen from FIG. 7.

The function of the clutch slip with active modulation, i.e., clutchslip mode 2, is determined by the following parameters.

One parameter is the vibration mode. The optimal curve of thetransmittable clutch torque over time depends on the curve of therotational irregularity of the main order at the clutch input. In thepreceding example, the assumed excitation was purely sinusoidal as wasthe optimal curve of the modulated clutch force. In an actualpowertrain, the main order of the alternating torque at the clutchinput, which has already been pre-decoupled, has an at leastapproximately sinusoidal shape so that the modulation of the clutchtorque can also be described by a sine function in this case in order toachieve good results as is shown in FIG. 11. However, other harmonic andnon-harmonic functions can also be taken as a basis such as, forexample, a trapezoidal curve as is shown in FIG. 12. The vibration modecan also be optimized to reduce a plurality of engine orders. In asimple case, this is possible in that the modulation is described by asuperposition of two sine oscillations, where one sine oscillation hasthe firing frequency, for example, and the other has the doubled firingfrequency.

However, dividing the actuating force of the clutch into a force F0,which is predefined via the slip controller and constant at thestationary operating point and a dynamic force Fa for modulation of thetransmittable torque, is mainly a conceptual model for describing theworking principle of the invention. It is a matter of designimplementation whether two forces are actually superimposed, e.g., inthe sense of two separate actuators, whether the force which anindividual actuator applies to the clutch is varied in a correspondingmanner, or whether combination forms are used.

What is decisive for the method is only that the transmittable torque ofthe clutch is changed dynamically in a suitable form and with suitableparameters. For tuning to the main engine order, the modulationfrequency must correspond to the firing frequency of the internalcombustion engine. Therefore, it increases as a function of enginespeed. In a 3-cylinder 4-stroke engine, for example, for the speed rangefrom 1000 RPM to 2000 RPM, a modulation frequency of 25 Hz to 50 Hz isnecessary. In engines with cylinder deactivation, it is particularlyadvantageous when the adjustment of slip actuation allows switchingbetween the orders of the full range and the deactivation range.Configuring to higher orders or a combined configuration to a pluralityof orders is also possible.

The optimal phase of the modulation amounts to 180° in relation to thevibration of the input speed of the slip arrangement as has already beendescribed above in the theoretical derivation of the function. Phaseshifts in the range of 180°±45° are particularly advantageous. If thephase shift is too small, the rotational irregularity is magnified andreaches a maximum at phase equality.

FIG. 14 shows different values in the powertrain of a motor vehicleaccording to FIG. 4 for three different cases:

Column 1: slip mode 1Column 2: slip mode 2—phase in a favorable rangeColumn 3: slip mode 2—phase in an unfavorable range.

The speed at the input area 31 of the slip clutch 30 is shown in eachinstance in the top line. Owing to the rotational irregularity of theinternal combustion engine, the speed fluctuates around a mean speed, inthis case ˜1205 RPM, in spite of pre-decoupling, e.g., through a DMF anda speed-adaptive damper 6 (compare this arrangement with theconstructions in FIGS. 5 and 6). For the sake of clarity, theoscillation of the speed in an engine firing order is also shown inaddition to the raw signal. This can be determined by means of fastFourier transformation from the time curve of the total vibration.

The slip speed ns between the input side 31 and output side 32 of theslip clutch 30 and the active torque Ma are shown in the second line.The active torque Ma is directly proportional to the above-mentionedactive force component Fa and is calculated as: M_a=F_a··r·μ.

In the active slip mode 1 in column 1, force Fa and therefore alsotorque Ma are equal to zero. Accordingly, the occurring slip curve isthe result of the actuating force F0 adjusted by the slip controller toobtain a mean slip (in this case 5 l/min), the curve of excitation,i.e., the speed fluctuation or torque fluctuation at the clutch, and thecurve of the friction coefficient of the clutch over slip speed.

In active slip mode 2, a sine curve of force component Fa and of activetorque Ma with a determined amplitude and with the firing frequency ofthe internal combustion engine is given in columns 2 and 3.

In column 2, the phase relation of the curve of the active torque Ma tothe curve of the speed upstream of the clutch in firing order in thediagram amounts to approximately 180°. In other words, in the timedomains in which the speed fluctuation in firing order has minima, theactive torque Ma has maxima, and vice versa. This shows an optimizedtuning of active slip mode 2.

An unfavorable case in which the active torque runs approximately inphase with the speed at the input area of the clutch is shown in column3.

The diagrams in line 3 again show the torque transmitted by the clutchas original raw signal and as the component thereof in engine firingorder. It will be appreciated that the irregularity in the torque in themain engine order is almost completely rectified with active slip mode 2with optimized phase (see column 2). With the unfavorable phase (seecolumn 3), the amplitude of the torque irregularity is increased evenfurther relative to active slip mode 1 (see column 1).

However, the phase of the modulation need not be exactly 180° inrelation to the speed at the input of the slip mechanism to achieve apositive effect. In order to achieve an improvement over active slipmode 1, it is advantageous when the phase shift is in the range of180°±45°.

FIG. 15 shows the speed curve in the input area 31 of the sliparrangement 30 as is also shown in FIG. 14, middle column, top line, fora static operating point.

The input speed (ne) has a mean value (nem), in this case 1205 l/min,around which an alternating component (new), not shown here, oscillatesbecause it is congruent with the curve of ne. The curve of thealternating component substantially depends upon the character of theinternal combustion engine 50, in particular the quantity of cylinders,and the pre-decoupling. The alternating component can be described bymeans of fast Fourier transforms (FFT) approximately as superposedsinusoidal oscillations (newp_i). The lowest frequency of a periodicpartial oscillation of the alternating component of this kind is thefiring frequency of the engine. The frequencies of further harmonicoscillations have a whole number ratio with the firing order. In anactual powertrain, vibration components can also occur with a non-wholenumber relationship with the firing frequency, but this will not bedealt with here. The periodic alternating components in the main engineorder (newp_1) and in doubled main engine order (newp_2) are shown byway of example in FIG. 15. The amplitudes of the alternating componentsfluctuate between a minimum (newp_i_Min) and a maximum (newp_i_Max). Thecurve of an alternating component of this kind is a reference quantityfor the phase shift β of the modulation of the activation of the sliparrangement in order to achieve a reduction in rotational irregularityin the corresponding engine order.

There is an optimal amplitude of the active torque Ma which dependspredominantly on the mean engine torque of zeroth order and the meanslip speed. There is an approximately linear relationship between theoptimal amplitude and the mean torque in different load states.Amplitudes of modulation of the torque which can be transmitted by theslip arrangement of between 5% and 15% of the mean engine torque areparticularly suitable.

The efficiently operative friction coefficient particularly of a wetfriction clutch such as is commonly used in motor vehicle powertrainsdepends on the instantaneous differential speed between the input andthe output of the clutch. Usually, the curve is significantly adaptedthrough additives in the oil and through the material and geometry ofthe linings so as to result in a degressive slope over the slip speed. Atypical friction coefficient curve is shown in FIG. 16.

For the slip clutch proposed herein, it is particularly advantageouswhen the friction coefficient lies in a range of between 0.05 and 0.15and rises steeply up to a highest possible slip speed. Slopes of thefriction coefficient over speed of between 0.001/RPM and 0.005/RPM in aslip range up to 30 RPM are particularly favorable. The mean slip speedis adjusted by a slip controller. Since slip generally causes frictionlosses which must be dissipated in the form of heat energy, a smallestpossible mean slip speed is aimed for. Mean slip speeds of less than orequal to 30 RPM, particularly advantageously less than or equal to 10RPM, are advantageous for the actively modulated slip.

Active slip mode 2 brings about an appreciable improvement in decouplingcompared to the known slip mode 1 primarily in the low to medium speedrange. This has the advantage of reduced expenditure in the control andactuation of the slip clutch. Particularly at high speed and dependingon the vibration behavior of the powertrain, no slip may be necessary incertain operating states for the decoupling of rotationalirregularities. Therefore, it is useful to implement a needs-basedoperating strategy. This can be based on the following schema:

Low Speed Medium Speed High Speed High Load slip mode 2 slip mode 2 slipmode 1 Medium Load slip mode 2 slip mode 1 no slip Low Load slip mode 1no slip no slip

Particular operating states such as gear-dependent vibrational nodes,starting or resonances are likewise to be taken into account.

Thus, while there have shown and described and pointed out fundamentalnovel features of the invention as applied to a preferred embodimentthereof, it will be understood that various omissions and substitutionsand changes in the form and details of the devices illustrated, and intheir operation, may be made by those skilled in the art withoutdeparting from the spirit of the invention. For example, it is expresslyintended that all combinations of those elements and/or method stepswhich perform substantially the same function in substantially the sameway to achieve the same results are within the scope of the invention.Moreover, it should be recognized that structures and/or elements and/ormethod steps shown and/or described in connection with any disclosedform or embodiment of the invention may be incorporated in any otherdisclosed or described or suggested form or embodiment as a generalmatter of design choice. It is the intention, therefore, to be limitedonly as indicated by the scope of the claims appended hereto.

1.-8. (canceled)
 9. A method for transmission and damping of a meantorque (Mm) with a superposed alternating torque (Mw) in a torquetransmission arrangement for a powertrain of a motor vehicle having aninput area rotatable around a rotational axis (A) and an output arearotatable around a rotational axis (B), comprising: transmitting themean torque (Mm) with the superposed alternating torque (Mw) along atorque path (M) from the input area to the output area, wherein theinput area of the torque transmission arrangement rotates at an inputspeed (ne) around the rotational axis (A), and the output area of thetorque transmission arrangement rotates at an output speed (na) aroundthe rotational axis (B), wherein at least the input speed (ne) iscomposed of a mean speed (nem) and a superposed alternating component(newp), an alternating component (new) is a superposition of periodicspeed oscillations (newp_i) whose frequencies (f) have a substantiallywhole number ratio (i) with a firing frequency (Zf), each periodicoscillation (newp_i) has a minimum (newp_i_Min) and a maximum(newp_i_Max), providing a slip arrangement in the torque path (M)configured to transmit the mean torque (Mm) with the superposedalternating torque (Mw) and generate a speed slip (ns) between the inputspeed (ne) and the output speed (na); and providing, by the sliparrangement: a maximum of an external activation of the speed slip (ns)in an area of the maxima (newp_i_Max) of at least one periodicoscillation component (newp_i) of the superposed alternating component(newp) and a minimum of an external activation of the speed slip (ns) inthe area of the minima (newp_i_Min) of at least one periodic oscillationcomponent (newp_i) of the superposed alternating component (newp). 10.The method according to claim 9, wherein the external activation of theslip arrangement is carried out by a hydraulic unit.
 11. The methodaccording to claim 9, wherein the external activation of the sliparrangement is carried out by an electric unit.
 12. The method accordingto claim 9, wherein the external activation is suitable to provide, atthe slip arrangement, a modulation range of one of: from 23 Hz to 50 Hz,from 33 Hz to 66 Hz, or from 50 Hz to 100 Hz.
 13. The method accordingto claim 9, wherein the slip arrangement is configured as a startingelement.
 14. The method according to claim 9, further comprising:providing a starting element in addition to the slip arrangement. 15.The method according to claim 13, wherein the starting element isconstructed as one of: a friction clutch, a multiple disk clutch, ahydrodynamic clutch, a disconnect clutch in a hybrid drive, a dualclutch, a triple clutch, or one of a clutch or a brake in conjunctionwith a planetary gear unit.
 16. The method according to claim 9, whereinthe rotational axis (A) and the rotational axis (B) extend one ofcoaxially relative to one another and offset relative to one another.17. The method according to claim 14, wherein the slip arrangement isconstructed as one of: a friction clutch, a multiple disk clutch, ahydrodynamic clutch, a disconnect clutch in a hybrid drive, a dualclutch, a triple clutch, or one of a clutch or a brake in conjunctionwith a planetary gear unit.